TRH, LHRH, somatostatin, CFR and GHRF were isolated and characterized, and their synthetic preparations have become available. These hypothalamic peptides were considered to be the physiological hypophysiotropic hormones which regulate their respective target cells in the pituitary gland. However, our recent experiments have suggested that GH release is resulated not only by somatostatin and GHRF (rat GHRF43 in the case of rats), but also other unknown factor(s). Furthermore, we have isolated a peptide from ovine brain extracts which stimulates GH release in vitro and elucidated its partial amino acid sequence as HSDGIFTDSYKRYNKEMAK... On the other hand, PRL releasing factor (PRF) has not been isolated, though VIP and PH127 have been proposed as a PRF. Arguments relative to the pesence of FSHRH in addition to LHRH have not been settled. These problems have led us to decide to reexplore possible novel hypophysiotropic peptides in the hypothalamus by mapping active peptides as tested by non-specific hypothalamic activity as determined by cyclic nucleotide stimulation in comparison with known hypothalamic factors. If novel peptides are present, their specific hypophysiotropic activity will be determined and eventually isolated characterized, synthetized and studied for their physiological significance. In addition, we demonstrated CRF and GHRF activity in the gut. These substances will be examined for chamical and immunological characteristics in comparison with hypothalamic counterparts, and if a sufficient amount is present, they will be isolated, characterized and their physiological significance will be determined. Finally, the regulatory mechanism of the hypothalamic neurons which synthetize and release hypothalamic hormones, with a special emphasis on CRF and GHRF. These mechanisms will be investigated using physiological and immunohistochemical methods. The immunohistochemical work will be conducted using double staining method at electron nicroscopic level.